Earth inductor compass



pril 28, 1 936. I I U. GUERRA I EARTH INDUGTORQ COMPASS Filed Dec. 20, 192 1 Patented Apr. 28, V 1936 UNITED STATES PATENT OFFICE I 2,038,787 EARTH INDUCTOR COMPASS Ugo Guerra, Rome, Italy \pplication December 20, 1934, Serial No. 758,419

, In Italy December 28, 1933 3 Claims. (01. 33-20 4) My invention has reference to "a device for in space the sensitive part of the compass, and

finding the direction of the terrestrial magnetic lastly to obtain a complex, giving indications of field consisting essentially of an alternating curthe maximum possible precision, these indicarent generator having stationary windings, the tions not being subjected to be subsequently mod- 5 induction of which is provided by the terrestrial lfled by any cause depending from the working 5 magnetic field. By a suitable arrangement of or from the construction of the compass. This the electric circuits, the current produced allows latter has in fact the electric circuits set conto obtain at a distance the indications relative to tinuously without interruptions, and rigidly'conthe orientation of the place or of the vehicle connected, as there are no brushes, nor collectors, nor

taining the device, and also to determine the dirotating windings. 10 rectlon which the said vehicle must follow. I The generating part of the current, being of The variation of the induction which is necesthe type of rotating ferromagnetic field, producsary to generate the current is obtained by a ing alternating currents, the indicator must thereperiodic variation of the air gap between a cerfore be electro-dynamical, but in order to improve tain numberof cores made with magnetic mathe damping and to increase the sensitiveness of 15 terial forming the inductors, having preferably the compass, it is preferable to use instruments 8. high permeability, disposed so as to face each of the continuous current type by the unidirecother, and traversed more or less by the path of tional rendering of the current coming from the the earth's lines of force, according to their potentiometer device. In all the embodiments 2Q orientation in the magnetic field, and also proof the compass hereinafter described, the use of vided with windings in which currents are ina continuous current instrument is mentioned, duced due to the said variation of the magnetic but it should be understood that an electro-dyflux; the indication of the direction is obtained namical instrument may be used indiiferently, by the method of reducing to naught the currents whenever the current is not made unidirectional,

5 traversing the indicator, the control or the deand the field of the same instrument is fed by an termination of the course being obtained by prealternate current having a fixed phase and the disposing the course on a potentiometric device same frequency. electrically and s 'tably-connected both to the Figs. 1-4 of the accompanying drawing reprecurrent generator and to the circuit of the indisent by way of example four different schematic cator. In this latter element the current will circuit diagrams, suitable to realize the compass 30 vanish when the compass, which remains always forming the object of the invention, while Fig. 5 fixed relatively to the axis of reference of the shows a rotor system anda synchronous mechanvehicle on which it is mounted, will have rotated, ical switch suitable as a circuit breaker.

together with the vehicle, through an angle, rela- In Fig. 1 showing the scheme of its elementary tively to the direction of the earth's magnetic base, 35 field, such as to cause, with the currents induced 1-2 and 3-4 indicate two pairs of inductors in the windings, a resulting current which is and rectilineal cores made of magnetic material, naugh at the terminals of utilization of the pohaving preferably a high permeability, disposed tentiometric device. Such arrangement has for at right angles to each other. 5 is a toothed rotor 40 its object the elimination of distance mechanical made of the same material, the rotation of which 40 controls which are usually used in induction comproduces simultaneous and successive reductions passes, and the possibility of disposing the course and increases in the air gaps disposed between control at any distance desired, and to render the the inductors of the two pairs. i, 2', 3 and 4', control indications absolutely proportional to the are single electric windings on the various inangles ofdisplacement of the compass in the ductors, disposed either in series or in derivation 45 earth magnetic field. Said arrangement has furbetween them, relative to the windings of each ther for its object to cause the said indications pair of cores; 2|, 22 are the terminals of the cirto be absolutely independent of the frequency of cuit formed by two windings of the pair of inducvariation of the induction, as the potentiometric tors l, 2; and 23, 24 are the terminals of the cir-,

0 control may be exclusively ohmic; toobtain a cuit formed by the windings of the pair of induccompass having a high sensitiveness, and to allow tors 3 and 4. An annular closed winding having the use of an instrument having a high directing a suitable ohmic resistance or impedance, is fed torque, it being possible to increase the number at four diametrically opposite points 3|, 32, 33, of the inductors as well as that of the windings and 34, by two circuits H, 22, and 23, 24, in th as these latterare fixed: to balance magnetically way indicated in Fig. 1, so that the four portions: 5

3l-33; 33-32; 32-34; and 3l-3l, may be exactly equal to each other both geometrically and electrically. 9 and III are two. slides which are diametrically opposite and integral one with the other, these slides being adapted to move along and in contact with an edge of the annular winding 8. ll indicates a continuous current instrument having its zero mark disposed on its centre, connecting electrically the two slides 3 and III with each other.

In this arrangement, i1 i3 represents the direction of the horizontal component of the earth magnetic field, disposed by way of example in a direction parallel to the bisector of the angle formed by the two pairs of inductors and 3-4, said inductors will be traversed equally by the fiux, so that the rotation of the toothed rotor 5, which produces an equal variation of reluctance in the two pairs or inductors, will generate, in the windings l', 2' and 3', 4', alternate currents of equal amplitude. If at any point of the two circuits Zl-22 and 23-24, two synchronous rotating switches 5 and 1 are inserted with the rotor 5, so as to allow the passage of a single alternation of the current, the said two circuits will be traversed by two unidirectional currents having the same amplitude. To the four terminals of the potentiometric circuit 8, will be applied consequently two equal electromotive and unidirectional forces, and consequently it will readily be seen that, due to the polarities as shown by way of example in Fig. 1, there is only one. diametrical position of the pair of slides 3 and III, in which the resultant eil'ect oi the currents traversing the indicator II, and particularly the position indicated in said figure, viz., 45 between the diameters 3|, 32 and 33, 34, is reduced to}. Any other position of the slides, which zero. does not differ 180 from the first, will cause the deviation of the indicator in either direction, the maximum deviation being reached in the position of from that in consideration; the indicator will however be equally deviated it the two pairs of inductors of the generating portion will shirt from the position indicated relative to the earth magnetic field, as in such case the bal- .ance of the currentsinthe potentiometric circuit becomes broken. It will also be seen that, it it is desired, for example, to follow a direction at an angle 01' 45 from the direction considered, it will be necessary, for example, to place the pair of slides 9 and I 0 on the diameter 33-34, and rotate the generating part also through an angle of 45, in order to obtain a resultant current which is nil on the indicator I I which means that the pair of inductors 3 and 4 will have to dispose itselt normally to the direction of the earth magnetic field to obtain that the E. M. F. becomes nil on the respective windings.

The above considerations may be extended to all the possible positions of of slides 9 and I0 inside the potentiometric ring 8, and consequently to all directions; it follows from this, that to anyangular displacement oi the slides, there is a corresponding similar angular displacement that must be imparted to the.

compass in order to reduce to naught the resulting current inside the indicator instrument. It the pair of slides carries an index finger movable on a dial I2 graduated as'a compass rose, the predetermined direction maybe fixed directly on said graduated dial. There is a-direct linear relation between the angles'of displacement ofthe pair of slides and the corresponding'angles of the compass, which give no current'in the indicator.

the diametrical pair By a suitable proportloning of the windings l', 2', 3', and l, and the resistance or impedance of the potentiometric winding 8, the distance betwen this latter and the compass may be selected as desired.

Fig. 2 shows a simplified arrangement in which the tworotating switches 6 and 1 shown in Fig. 1 are reduced to a single rotating switch l6, which is no longer inserted on the winding circuits, but is inserted in the circuit of the slides 9 and Ill and the indicator II. It is obvious, in fact, that it is sufficient that only the indicator instrument be traversed by an unidirectional current. This arrangement is preferable to the one first described, both because the principal circuits are all traversed by alternating current, the characteristics of which may be varied by -means oi. suitable transformers, and also bescribed is shown in Fig. 3, which shows the rotating switch disposed in parallel, instead of in series, with the indicator, and the resistance for the variation of the sensitiveness is disposed in series, instead of in parallel, the whole giving similar results. All the arrangements above described require the use of synchronous rotating or vibrating switches, because, for the p rp se of permitting the indications of displacements from the 00'. ;:se in the two directions, it is necessary that the current, although unidirectional, may traverse the circuit of the instrument indifierently in either direction, which is' the feature of all mechanical switches.

A diilerent arrangement, providing the use of a single fixed rectifier, instead oi a mechanical one, for example a metallic oxide rectifier, a. diode and the like, is shown by way of example in Fig. 4, which shows that in the circuit of the slides 3 and ill, a fixed rectifier I9 is inserted instead of the indicator. This rectifier, which is of the difierential type with continuous current, for instance with crossed coils l8 and I8", is inserted in both circuits of the two pairs of windings, for example, in the way shown in Fig.v

4; it will be seen that, while the instrument'is always traversed by alternate currents having no effect, with regard to the continuous current, the resultant e'ifect will be naught only for a single diametrical position of the slides 9 and ill of the ring 8. This applies, of course, for av three inductors, instead of four as shown by way of example in Fig. 2, and by the symmetrical placing or the three inductors, viz. at be aoasna':

tween them, the generating portion will operate as a three-phase alternator, instead of a twophase alternator, and it will be suflicient therefore to connect the three windings of the inductors as a star or triangle connection. and to apply the corresponding circuit at three equidistant points of the potentiometric ring}, in order that the complex may function exactly as described in the arrangement comprising four inductors. Thus these latter may also be more than four, and it will be sumcient toprovide the potentlometric ring with an equal number of feed points in order that the operation of the device may be similar to that above described.

As shown in Fig. 5, the rotor and the synchronous mechanical switch may be mounted on the same axis, the device being rotated by any convenient means desired. According to Fig. 5, the shaft 20 carrying the rotoris rotated by an air jet 2| playing against the peripheral blades 22 of ,a disk secured to the upper end of the shaft.

- On its lower end, the shaft 20 carries a' polygonal cam 23, which. upon the rotation of the shaft,

; causes inrapid succession the opening and closing of the electrical contact 16, which is continuously pressed against the cam 23 by a spring 26.-This device requires only a very small amount of energy for imparting movement to generating alternating currents in said windings.

an annularclosed winding fed by said circuits at geometrically and electrically equidistant points corresponding in number to said windings or a multiple thereof, a pair of rigidly connected slides disposed diametrically opposite to each other and adapted to slide in contact with said annular winding for angular displacement, and

an indicator electrically connected with said slides and normally indicating the zero position.

2. The combination as specified in claim 1, in- I eluding synchronous rotating switches operatively associated with said rotor and included in said circuits causing two unidirectional currents having the same amplitude to traverse said circuits.

3. The combination as specified in claim 1, in-

.cluding a rectiflerin said circuits for rendering the alternating current produced by the generator unidirectional.

' v .nao GUERRA. 

